These days, it seems like everyone wants to get back a piece of their youth. Whether it's adult coloring books or wine in juice boxes, nostalgic products and events are everywhere. But alongside all the fun things that come with being a child, there are also restrictive rules and a strict bedtime. Being an adult is great because we can eat ice cream for dinner, watch R-rated movies, or fill our apartments with playpen balls if we want

The National Building Museum in Washington D.C. recently filled their 10,000-square-foot Great Hall with white playpen balls for guests of all ages to play in. The event looked like great fun, but if you missed it, please know you can recreate it in your own living space. 

It's safe to assume the only reason why you're not reading this from the bottom of a ball pit right now is because you don't know how many balls to buy. It's risky committing to purchasing a bulk order of playpen balls only to realize you can't actually afford to fill the whole room. Or what if you buy too many? This special calculator will make sure you know exactly what you're getting into. 

Inspired by this xkcd comic, the calculator takes a number of factors into consideration—such as apartment area, packing efficiency, and the radius and price of each ball—and then calculates how much money your personal ball pit will set you back. The website will either save you from a costly mistake or illuminate a very affordable way to double your property's worth. 

If you need the metric system, please see the Berge version. And if you're looking to actually put this calculator to use, these balls should do the trick